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Fossil Fuel Sustainability: When Will Fossil Fuels Run Out?


No emphasis is too great regarding the predicament of fossil fuel usage. The question has always been “when will fossil fuels run out” not “if” they will. It’s good that the drive to make renewable energy cost-efficient is making headway. 

Fossil Fuel Sustainability: When Will Fossil Fuels Run Out?

Care about the longevity of the environment means getting away from these second-rate energy sources ASAP. The rest of the world is starting to wake up, slowly, to the realization of this fact.

Renewable energy both pollutes less and lasts longer. The cost decrease over time has a real chance of being more affordable, too.

Even the United States, the single largest user of world energy (and the majority of that is fossil fuels) is seeing a decline in use. So, how much time is left to make this transition? Read on for a full breakdown.

Fossil Fuel: Defined

Are fossil fuels renewable? Not really. They do replenish, over a million years or so, but that doesn’t count.

Remember that fossil fuels and renewable energy are not the only two categories out there. Nuclear energy isn’t a fossil fuel but also isn’t renewable. 

Fossil fuels by definition are any of the fuels that were formed from once-living organic matter. Through a process of lithification and decay and millions of years, these materials became coal, oil, and natural gas.

They range in their efficiency and their pollutant capacity. One important factor to keep in mind is energy density. The reason that fossil fuels are so easy to use is that they are transportable and pack a punch.

A certain set of conditions are needed to produce them but they can be used anywhere. These facts play a role in shaping the world’s dependency. 

When Will Fossil Fuels Run Out?

How long a substance lasts depends on two key factors: reserves and usage rate.

Loss and transformation both fall into the reserves category. This is important as some fuels are more likely to be lost in transport than others. 

Reserves also come in different categories. The total resource number represents all known amounts.

These amounts get categorized into proved reserves, which are economically viable to extract. Next is probable reserves, these have been shown as probable but not viable. Last, are possible reserves, these will have less than 50% returns for the effort.

Usage rates further get modified by the efficiency of the equipment consuming them. In making future estimates linear progressions of previous improvements are used. These numbers are viable barring any sudden leap in technology.

This guide will also explain briefly how fossil fuels are formed.


The original fossil fuel, coal has the advantages of being easy to get to and simple to use. Think of the energy released from burning wood or other plant matter. 

Then consider how much more you can get out of charcoal, which is partially burned wood under pressure. That gives you some understanding of the energy density found in coal. 

While coal is easy to get to, it isn’t safe to get to. The product aerosolizes as it is dug out creating breathing hazards and water contaminants. 


Russia, China, India, and the United States, as well as other lesser coal-producing countries, hold a total of 1.1 trillion tonnes of coal.


Coal usage continues to increase across the world. However, this increase is slow in comparison to other fossil fuels and has been slowing further. Numbers from 2015 reflect a 0.4 percent increase. 

Production decreased a total of 0.7 percent in that same time.

Following these trends and accounting for increases in India, which has a booming energy need, coal will last 150 years.


Oil is more difficult to retrieve than coal. The underground reserves of oil need drilling and pumping mechanisms. The crude oil then needs to be processed and refined before use.

Oil comes from marine organisms along the seafloor that decay and accumulate. As they accumulate they infiltrate cavities and create bubbles in the seafloor which then wall off. 

Further types of oil are pulled from oil sands and shale oil through chemical processes. 


Oil figures get monitored more closely than coal. These show that 1.665 trillion barrels of oil remain as of 2017. The single largest of these reserves exists in Venezuela. 

As expected, the Middle East, as a whole, still holds nearly 65% of the world’s oil.  


The problem with oil is that it also has industrial uses outside of energy. The other two fossil fuels get used primarily, if not exclusively, for energy. 

These uses accelerate oil consumption worldwide.

Oil consumption rose 2 million barrels per day in 2014 over the average. With over 36.6 million barrels being used per day the world reserves will deplete in 50 years.

Another 30-40 years’ worth of oil exists in hard-to-extract oil sands and shale oil mostly in the United States and Canada.

Natural Gas

Of all the fossil fuels, natural gas is most arguably renewable. While the large deposits come from long-dead micro-organisms much the same as oil, not all of the sources need to be ancient. Livestock and landfills pump out methane which is natural gas.

These sources could be tapped (and should be eliminated as greenhouse agents) to increase natural gas reserves.


Current figures from 2017 indicate 6,023 Tcf (trillion cubic feet) of natural gas exists. The vast majority of these reserves require extra processing to reach. 

The largest reserves exist in the United States, Nigeria, and Algeria.

Most natural gas can’t be reached with simple drilling and tapping but requires hydraulic fracturing to get to deposits.


Demand for natural gas increases faster than other fossil fuels. The fuel works well for creating heat and energy and also burns cleaner than coal or oil. 

Green-conscious countries increase demand. The tech to use the gas has come a long way since 1940.

Even without capturing livestock and landfill sources, natural gas is expected to last 400 years at current rates of use. 

Knowledge is Energy

Understanding the changing energy needs of the planet, and the changing technology gives a complete picture. Adoption of renewable sources will have a direct, but unknown impact on these figures.

When will fossil fuels run out? Hopefully never. Hopefully, the world will move on before they are gone in the first place. 

Earthava Team
Earthava Teamhttps://www.earthava.com
A collective of experts in Renewable Energy, environment and green living. Some of these content are written by AI But revised and edited by the team.

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